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Home >> Chemistry Dictionary >>Glass Electrode - Glyoxal
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G factor.
The proportionality factor in the relation between the magnetic moment μ and the number of. Unpaired electrons.
Μ = g √s(s+1)
Sometimes called the gyromagnetic ratio. For a free electron g =2.003.
Gibbs’ equation of surface concentration.
This equation release the surface tension (g)of a solution and the amount (Г) of the solute adsorbed at unit area of the surface. For a single non – ionic solute is dilute solution the equation approximates to
Г = cdg/RTdc (where c is the concentration per unit volume and R is the gas constant).
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Gibbsite.
A mineral form of hydrated aluminium hydroxide, Al(OH)3.
Giga.
Symbol G. A prefix used in the metric system to denote one thousand million times. For example, 109 joules = 1 gigajoule (GJ).
Glass.
In general a supercooled liquid which forms a non – crystalline solid. Specifically a hard brittle, amorphous material which is usually transparent, or translucent and resistant to chemical attack.
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Glass electrode.
A type of half cell having a glass bulb containing an acidic solution of fixed pH, into which dips a platinum wire. The glass bulb is thin enough for hydrogen ions to diffuse through. If the bulb is placed in a solution containing hydrogen ions, the electrode potential depends on the hydrogen –ion concentration. Glass electrodes are used in pH measurement.
Glass fibres.
Melted glass drawn into thin fibres some 0.005 mm – 0.01 mm in diameter. The fibres may be spun into threads and woven into fabrics, which are then impregnated with resins to give a material that is both strong and corrosion resistant for use in car bodies and boat building.
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Glass filter.
A porous glass disk or plate fused into a glass cylinder or funnel. It is widely used for filtering.
Globin.
A protein, belonging to the histone class. Combined with haem it form the respiratory pigment haemoglobin.
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D – glucose, dextrose.
C6H12O6. The most common hexose sugar. It is present in many plants, and is the sugar of the blood. It is a constituent of starch, cellulose, glycogen, sucrose and many glycosides, from all of which it can be obtained by hydrolysis with acids or enzymes.
Glue.
A colloidal mixture of proteins, built up from aminoacids prepared from animal or fish waster treated first with milk of lime, acidified and then heated with water at about 600C. Glue is related to gelatine. An aqueous solution is used in flocculation, recovery of suspended particles. Hide glue (80%) forms a gel in glycerol which can be used in print rollers and in shock absorbing equipment.
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Glutamic acid,
α – aminoglutaric acid.
Gluten.
A mixture of proteins obtained from wheat dough by washing out the starch. It contains mostly the two proteins gliadin and glutelin.
Glycogen
(animal starch). A polysaccharide consisting of a highly branched polymer of glucose occurring in animal tissues, especially in liver and muscle cells. It is major store of carbohydrate energy in animal cells and is present as granular clusters of minute particles.
Glyoxal,
ethanedial, biformyl, CH(O).CHO. Crystallizers in yellow prisms; its vapour is green and burns with a violet flame; m.p.150C, b.p.510C. Readily polymerizes on standing in the presence of moisture; the aqueous solution contains the dihydrate. It can be manufactured by oxidation of ethylene glycol with air using a copper oxide catalyst. Used to harden photographic gelatin.
Goethite.
A yellow –brown mineral, FeOH, which is crystallizing in the orthorhombic system.
Gold.
Symbol Au. A soft yellow malleable metallic transition element; a.n. 79; r.a.m. 196.967; r.d. 19.32; m.p. 1064.430C; b.p. 2807 ±20C. It is found as the free metal in gravel or in quartz veins, and is also present in some lead and copper sulphide ores. It also occurs combined with silver in the telluride sylvanite, (Ag, Au) Te2. It is used in jewellery, dentistry, and electronic devices Chemically, it is unreactive, being unaffected by oxygen. It reacts with chlorine at 2000C to form gold (III) chloride. It forms a number of complexes with gold in the +1 and +3 oxidation states.
Gold (III).
Chloride (Auric Cutoride, AuCl3); A brown mass, deliquescent and readily dissolves in water. It is used in electroplating and in photography as a toning agent.
Gold grains.
198Au encapsulated in platinum used as a radiation source.
Gold, standard.
Pure gold is too soft for use as ornaments or for coinage, and is alloyed with copper or silver, or both. The fineness is expressed either in parts per thousand, or in carats. Pure gold is 24 carat fine, and the five standard alloy of 22, 18, 15, 12 and 9, i.e. parts of gold in 24 of alloy, are legalized.
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